Electrophotographic imaging devices, such as laser printers, fax machines, and photocopiers, are designed to produce an image on a print media, such as a sheet of copy paper. Electrostatic imaging devices generally include a photoconductive element that is selectively illuminated by a scanned laser beam or light emitting diode arrays in response to data representative of a desired image that is to be produced, wherein the incident light generates an electrostatic copy of the desired image on the photoconductive element. The electrostatic copy is then developed by first exposing the photoconductive element to toner powder that adheres to the charged portions of the photoconductive element and subsequently transferring the toner powder from the photoconductive element to the print media. The “loose” toner powder is then fused to the print media by a fuser unit.
Fuser units typically employ a combination of heat and pressure to fuse the toner powder to the print material. One common type of fusing unit comprises a pair of opposing rollers that form a fusing nip, with one roller serving as a fuser roller and the other roller serving as an idler pressure roller. By convention, the fuser roller is generally the roller that contacts the unfused toner and is the roller having the higher temperature if there is a temperature differential between the rollers, and the idler pressure roller applies pressure at the fusing nip to hold the print media in contact with the fuser roller. The fuser roller is generally heated while the idler pressure roller may or may not be heated.
To fuse the loose toner to print material, the print material is fed through the fusing nip at which point the fuser roller melts the loose toner and permanently affixes it to the print material. Fuser units are generally maintained at temperatures between 150° C. and 200° C. in order to properly fuse the loose toner to the print material. As a result, fusing units store a large amount of heat energy and can potentially continue to do so long after the associated imaging device is powered-off. In some instances, the heat energy stored in the fuser unit can be so large that some surfaces of the fuser unit can remain at very high temperatures for several tens of minutes, potentially even after the fuser unit is removed from the imaging device.
These high temperatures represent a potential burn hazard for individuals who may attempt to access the fuser unit. Presently, printed warning labels are placed at conspicuous locations on the fuser units to warn users of the potential burn hazard. However, such warnings are not indicative of whether the fuser unit is presently at a high temperature and are not always sufficient to prevent burns.